Disconnect between s6-svscan and s6-rc

[Ihor Antonov <ihor@antonovs.family>]

Hi Skarnet Supervision Gang :)

I want to run a thing buy you, to udnerstand whether I am not
understanding something or misusing something or is there actually a
problem. Here it goes:

When I do

    s6-rc -u change myservice

the command hangs, waiting for the service to start, keeps the ftfrig
pipe open...

The service does not start, because there is an error in run script.
This can't be caught by compilation phase, in my case there was a
missing env var that prevented a service to start, but I imagine there
can be all sorts of issues with run scripts.

The user of s6-rc gets no error message, and waits forever.
The error message is captured by s6-svscan (or a corresponding logger
for that service) and is either saved into a log file, or printed to a
tty on which svscan is running. 

The user is almost never on the same tty with svscan. The user never
gets an error message from the service, unless they explicitly know
where to look.

It would be nice if a user can get a temporary view into the service's
stdout for the short duration of s6-rc execution? Such that when s6-rc
never exits waiting we can see what the error message that service
prints? 


Thanks

Ihor